Could Corn be Tasselling by June?

Many—but not all—corn producers in Iowa and Illinois are playing it safe when it comes to this year’s rising soil temperatures and record-high ambient temperatures.

"It’s unprecedented to have this much area ready to plant," says Emerson Nafziger, crop specialist at the University of Illinois, Urbana. "If the calendar said ‘April’ instead of ‘March,’ there would be no holding back." Last spring’s wet field conditions, which led to late planting and lower yields in Illinois, are still fresh in the minds of producers who for the most part are still showing planting restraint.

Illinois and Iowa producers who plant this early are taking a risk. "The soil temperatures are up but the risk of frost between now and the middle of April is high," notes Roger Elmore, extension corn specialist at Iowa State University, Ames.

A late killing frost is the biggest threat to planting in March. Iowa producers who plant before April 11 would not be able to collect on their crop insurance policies if a frost were to require they replant their fields, says Elmore. In Illinois, Nafziger says the cutoff is April 6.

"To maximize yields, Iowa producers should start planting April 11 at the earliest," says Elmore. "The window of opportunity runs to the ninth or tenth of May for producers to get within 5 percent of maximum yields." Planting recommendations run as late as May 18 in the northwestern and central parts of the state. Dryness in northwestern Iowa also means soils would cool quickly if a frost were to hit.

Soil temperatures in Iowa are already in the high 50°s F. and are rapidly heading into the 60°s, according to data collected by Iowa State. "Soil temperatures are off the charts in terms of where they are relative to previous years," says Elmore.

With ambient temperatures in the 70°s and 80°s and the majority of soil in good condition in both states, corn will emerge quickly. "If the crop is up and we get a 30° night, it would mean serious replanting," says Nafziger.

In 2005, a late widespread freeze resulted in a large share of replanting. That year, Palle Pederson, agronomist at Iowa Sate University wrote on his website: "What a weekend! It was only 10 days ago that it was in the 70°s, and yesterday (May 1), I finally stopped planting when it started to snow."

The National Weather Service’s Climate Prediction Center’s outlook through April 1 calls for above-average temperatures in both Iowa and Illinois, with above-average rainfall in the northern half of Iowa and average to below-average precipitation in the southern half of Iowa and throughout Illinois.

"I’ve been around long enough that I’m not going to tell them not to plant," says Nafziger. He adds that if he were an Illinois corn producer he wouldn’t plant just yet but he probably wouldn’t wait for the April 6 insurance date either if the weather remains balmy. If a lot of growers plant early, it could actually shift the crop cycle. "We could have a crop that is tasseling by the middle of June," he says. "If it stays dry and we get another 1988, planting now could be better than planting in a month from now."